Superlettuce! Extreme weather calls for extreme crops

Modern Farmer

Monday, September 30th, 2013

Itâ€™s hot. By 9 a.m., a dusty desert film radiatesÂ hazy stillness over thirsty fields of produce. TheÂ air is dry as static, and temperatures are well onÂ their way to a blistering peak of 103 degrees in theÂ desert town of El Centro, California, 13 miles fromÂ the Mexican border. But Beiquan Mou, a researchÂ geneticist with the U.S Department of Agriculture,Â is buoyant, because his acre-wide field of greenÂ and purple lettuce is thriving in these oven-likeÂ conditions.

Lettuce is a delicate mistress; it must be coddledÂ and kept below 85 degrees or it will struggle â€”Â bad news for Americaâ€™s salads, as scientists claimÂ climate change is poised to turn central California,Â home to the nationâ€™s â€śsalad bowl,â€ť into a dust bowlÂ by the end of the century. Most of the year, 60 percentÂ of all the lettuce Americans consume growsÂ in the Salinas Valley, 500 miles from here, cooledÂ by the Pacific breeze. Temperatures there hoverÂ at an average of 68 degrees. In El Centro, highs ofÂ 106 are not unusual. And that is why Mou is here.Â Someday, much of Americaâ€™s prime agriculturalÂ land will be subject to the same weather conditionsÂ that conspired to make 2012 the hottest year onÂ record in the continental U.S. Over the course ofÂ this century, North America will see longer periodsÂ of extreme heat. Farmers could see annual losses ofÂ $5 billion or more.

Since 2010, Mou has been on an epic quest forÂ the worldâ€™s most heat-tolerant lettuces. BackedÂ by a three-year federal grant, part of a $38 millionÂ effort to cope with climate change, he has growtestedÂ more than 3,500 varieties of lettuce andÂ spinach in a heat chamber laboratory, exposingÂ them to scorching temperatures and recording theÂ results. The goal: Identify the hardiest species, andÂ isolate their survival genes.

Someday, hopefully, the winners of this gladiatorialÂ death match will wind up on salad plates.Â The lettuce of the future may look and taste theÂ same, but thanks to the research Mou has begun,Â its DNA will contain a heat-resistant gene to helpÂ farmers cultivate it pretty much anywhere â€” evenÂ the desert.

By late May, Mouâ€™s 84 finalists â€” 28 icebergs,Â 28 romaines and 28 butterheads â€” are ready to beÂ picked and analyzed. They even have superheroÂ names like Gladiator, Jericho, Sniper and Invader.Â Crouching in pristine, button-down ensembles,Â Mou and his assistant pile lettuce heads intoÂ containers and carry them back to their shade tent.Â They weigh them, test their firmness, split themÂ open and measure their cores, taking note of tipÂ burn and leaf stress.

Measuring lettuce / Julia Scott

Many of Mouâ€™s plants have grown into mutantÂ parodies of supermarket lettuce. Some green-leafÂ varieties are more than a foot wide with heads biggerÂ than wedding bouquets. Others have cooked inÂ the sun so long they look like burnt marshmallows.

The weirdest-looking lettuces have shot theirÂ stems 2Ăł feet into the air, growing leaves in theÂ shape of Christmas trees. Called â€śbolting,â€ť this is aÂ survival tactic in which lettuce under heat stressÂ tries to flower quickly in an attempt to reproduce.

But Mouâ€™s lettuce has to do more than lookÂ good. He bites into a tasty-looking iceberg cultivarÂ called Glacier and makes a face. It is piercingly bitter.Â â€śIn the Salinas Valley, that one tastes just fine,â€ťÂ he says, shaking his head. He uses his knife to slitÂ open a neighboring iceberg. He nods in approval.Â Itâ€™s sweet. It will take trial and error to produce aÂ lettuce that is both hardy and tasty.

Global warming will dictate the worldâ€™s saladÂ bar selection in the not-so-distant future, and MouÂ isnâ€™t the only one rushing to condition our unpreparedÂ produce.

One of the USDAâ€™s top objectives in comingÂ years is to identify crop varieties with the mostÂ resilient all-weather genes. In addition to Mouâ€™sÂ work, USDA plant physiologists in North CarolinaÂ are looking for soybean cultivars that can tolerateÂ elevated ozone and carbon dioxide levels. InÂ Wisconsin, scientists are adapting cranberries toÂ unexpected frost snaps â€” another regional effectÂ of climate change. In Maryland, researchers areÂ studying crops that deliver better yields withÂ higher levels of carbon dioxide.

Mou wonâ€™t have results until 2014. But findingÂ the worldâ€™s first superlettuce is only half the challenge.Â It will take time â€” and money â€” to find aÂ way to crossbreed the lettuce genotypes with otherÂ existing strains. Charles Walthall, acting deputyÂ administrator of the USDAâ€™s Natural Resources andÂ Sustainable Agriculture Systems program, saysÂ industry leaders like Monsanto are already focusedÂ on similar research. Syngenta, for example, hasÂ taken an interest in Mouâ€™s study, and sent representativesÂ to one of his lettuce fields.

If all goes well, our lettuce may be more primedÂ than we are to survive the hot, dry times ahead.

â€śYou think this is hot?â€ť laughs Mou, sweating. â€śMaybe every day in the future will be this hot.â€ť